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Selection of heating elements for silicon molybdenum rod and silicon carbon rod of tubular furnace

    Silicon molybdenum bar electric heating element is a kind of resistance heating element based on molybdenum silicide. When the sintered molybdenum silicide products are heated to high temperature in oxidation atmosphere, a layer of dense quartz glass film is formed on its surface, which can keep the products from oxidation. Therefore, the silicon molybdenum rod element has unique high temperature oxidation resistance. The highest operating temperature is 1750 ¡æ. The resistance of the silicon molybdenum bar element does not change with the use time (the resistance increases with the temperature), that is, it does not age, so the new and old elements can be mixed. Like other ceramic products, the mechanical manufacturing of the silicon molybdenum bar element is brittle at room temperature, but it can be avoided if it is used properly and installed properly.
    Silicon carbide rod (distributed around the furnace)
    The carbon rod is a non-metallic high-temperature electric heating element which is made of green high-quality silicon carbide as the main raw material by light processing, high-temperature silicification and crystallization. Compared with the metal electric heating element, the element has the advantages of high temperature, oxidation resistance, corrosion resistance, long service life, micro deformation, convenient installation and maintenance, etc. The surface temperature of the heating part can reach 1450 ¡æ, which is negative from room temperature to 800 ¡æ, and positive characteristic curve above 800 ¡æ. Silicon carbide rod has good chemical stability, acid has no effect on it, but alkali and alkaline earth metal oxide have erosion effect on it at a certain temperature. At high temperature, water vapor, hydrogen, halogen and sulfur also have oxidation and erosion effects on it. In order to ensure that the furnace temperature bar bears even load, resistance must be allocated before installation to keep the resistance consistent ± 10%; during the long-term use of the electric furnace, when some bars are damaged due to other reasons and need to be replaced, the bars with appropriate resistance value shall be selected according to the growth of resistance value at that time, and can not be replaced with new bars. If the bars are damaged more or the resistance value increases too much, it is better to replace them with new ones when the required furnace temperature cannot be reached. The resistance of the replaced rod shall be measured again, and the resistance shall be distributed in the low temperature zone.